The present disclosure relates to a range extender for a hybrid vehicle which is driven by an electric machine, a drive for a hybrid vehicle and a motor vehicle having the drive.
A hybrid vehicle is known to be a vehicle which has at least two energy converters and two energy storage systems installed in the vehicle. The energy converters include, for example, electric motors, spark emission engines and diesel engines. The associated energy stores are, for example, batteries and fuel tanks. Hybrid vehicles permit fuel to be saved and at the same time the driving behavior to be improved.
Nowadays, the various hybrid concepts are differentiated in terms of the power classes of their electric drives as follows: micro-hybrid, mild hybrid, full hybrid or plug-in hybrid.
In addition, the following hybrid topologies are differentiated:                serial hybrid in which, for example, an internal combustion engine drives an electric generator which in turn makes available current to charge a battery or to drive an electric motor to propel the vehicle, wherein the internal combustion engine does not have a mechanical connection to the driven axle of the vehicle,        parallel hybrid in which either an internal combustion engine alone or an electric motor alone usually provides the propulsion of the vehicle, wherein the internal combustion engine can also drive the electric motor in the generator mode in order to charge the battery,        power-split hybrid which is distinguished by a planetary gear mechanism which can add the power of the electric motor and that of the internal combustion engine to one another.        
An internal combustion engine generator system, in particular in the case of a serial hybrid drive, is also referred to as a range extender.
DE 10 2010 002 168 A1 discloses a range extender for a vehicle which is driven by an electric machine, wherein the range extender has an internal combustion engine which drives a nine-phase generator. The generator feeds a nine-phase bridge rectifier with alternating voltage. The bridge rectifier generates a direct voltage which is applied directly to a lithium-ion battery via a two-conductor line for the purpose of charging. The lithium-ion battery in turn supplies energy to an electric motor in order to drive a vehicle. The known range extender is activated when the lithium-ion battery has reached a low state of charge. As a result, the range extender extends the range of the vehicle.
DE 10 2010 064 314, which was filed before the priority date of the present document and published thereafter also discloses a system for coupling a range extender to a controllable battery which is connected directly to an electric motor. The coupling of the range extender to the battery occurs either directly or via controllable switching elements.
In addition, controllable batteries which are connected directly to an electric motor are known from DE 10 2010 027 857 and DE 10 2010 027 861.